Two identical 20-mm thick plates are bolted to the top and bottom flange to form the built-up beam. if the beam is subjected to a shear force of v = 300 kn, determine the maximum spacing s of the bolts to the nearest mm if each bolt has a shear strength of 30 kn

Ohm's law tells you that i = v/r where v is equivalent voltage and r is equivalent resistance of the circuit
since all circuits have the same voltage, your question is really asking which circuit has the lowest total resistance, since the lower the resistance, the higher the current
circuit a has a resistance of 5 ohms; circuit c is in series so has a resistance of 10 ohms; circuit b is in parallel and therefore has a resistance of 2.5 ohms (review your notes on adding resistances in parallel and series); therefore b has the highest current

The answer is mean don't know

The  moon has  insufficient gravity to retain an  atmosphere. we conclude that the moon has no atmosphere  because its gravitational field is too weak to  have  retained any  atmosphere  that it had over times comparable to the age of the solar system.